It's just an observation that this switcheroo of Wallah/Voilà seems regional to that area of the world - would you say that's not true? No insult intended.

Other seemingly American conventions include saying: 'would of', 'could of', 'for all intensive purposes', 'I could care less', and plenty more. I travel to the US a couple times every month and notice things like this!

The implied insult is that this region is the only region where people are dumb enough to misspell these words.

All of your examples are examples of words and phrases that people have primarily heard (rather than read), and thus they spell them incorrectly. People who have read these phrases repeatedly are less like to make these mistakes of spelling.